Dennis Ritchie
Dennis Ritchie at the Japan Prize Foundation in May 2011
Dennis MacAlistair Ritchie

(1941-09-09)September 9, 1941
Diedc. October 12, 2011(2011-10-12) (aged 70)
Alma materHarvard University (BS)
Known forALTRAN
AwardsIEEE Emanuel R. Piore Award (1982)[1]
Turing Award (1983)
National Medal of Technology (1998)
IEEE Richard W. Hamming Medal (1990)
Computer Pioneer Award (1994)
Computer History Museum Fellow (1997)[2]
Harold Pender Award (2003)
Japan Prize (2011)
Scientific career
FieldsComputer science
InstitutionsLucent Technologies
Bell Labs
Doctoral advisorPatrick C. Fischer

Dennis MacAlistair Ritchie (September 9, 1941 – c. October 12, 2011) was an American computer scientist.[3] He created the C programming language and, with long-time colleague Ken Thompson, the Unix operating system and B programming language.[3] Ritchie and Thompson were awarded the Turing Award from the ACM in 1983, the Hamming Medal from the IEEE in 1990 and the National Medal of Technology from President Bill Clinton in 1999.

Ritchie was the head of Lucent Technologies System Software Research Department when he retired in 2007.

Early life and education

Dennis Ritchie was born in Bronxville, New York. His father was Alistair E. Ritchie, a longtime Bell Labs scientist and co-author of The Design of Switching Circuits[4] on switching circuit theory.[5] As a child, Dennis moved with his family to Summit, New Jersey, where he graduated from Summit High School.[6] He graduated from Harvard University with degrees in physics and applied mathematics in 1963.[5]


Ken Thompson (left) and Dennis Ritchie (right), in 1973
Version 7 Unix for the PDP-11, including Dennis Ritchie's home directory: /usr/dmr

In 1967, Ritchie began working at the Bell Labs Computing Science Research Center. In 1968, he defended his PhD thesis on "Computational Complexity and Program Structure" at Harvard under the supervision of Patrick C. Fischer. However, Ritchie never officially received his PhD degree as he did not submit a bound copy of his dissertation to the Harvard library, a requirement for the degree.[7][8] In 2020, the Computer History Museum worked with Ritchie's family and Fischer's family and found a copy of the lost dissertation.[8][9]

During the 1960s, Ritchie and Ken Thompson worked on the Multics operating system at Bell Labs. Thompson then found an old PDP-7 machine and developed his own application programs and operating system from scratch, aided by Ritchie and others. In 1970, Brian Kernighan suggested the name "Unix", a pun on the name "Multics".[10] To supplement assembly language with a system-level programming language, Thompson created B. Later, B was replaced by C, created by Ritchie, who continued to contribute to the development of Unix and C for many years.[11]

During the 1970s, Ritchie collaborated with James Reeds and Robert Morris on a ciphertext-only attack on the M-209 US cipher machine that could solve messages of at least 2000–2500 letters.[12] Ritchie relates that, after discussions with the National Security Agency, the authors decided not to publish it, as they were told that the principle applied to machines still in use by foreign governments.[12]

Ritchie was also involved with the development of the Plan 9 and Inferno operating systems, and the programming language Limbo.

As part of an AT&T restructuring in the mid-1990s, Ritchie was transferred to Lucent Technologies, where he retired in 2007 as head of System Software Research Department.[13]

C and Unix

Ritchie created the C programming language and was one of the developers of the Unix operating system. With Brian Kernighan, he co-wrote the book The C Programming Language, which is often referred to as K&R after their initials. Ritchie worked together with Ken Thompson, who is credited with writing the original version of Unix; one of Ritchie's contributions to Unix was its porting to different machines and platforms.[14] They were so influential on Research Unix that Doug McIlroy later wrote, "The names of Ritchie and Thompson may safely be assumed to be attached to almost everything not otherwise attributed."[15]

Nowadays, the C language is widely used in application, operating system, and embedded system development, and its influence is seen in most modern programming languages. C is a low-level language with constructs closely translating to the hardware's instruction set. However, it is not tied to any particular hardware—making it easy to write programs on any machine that supports C.[16] Moreover, C is a high-level language with constructs mapping to the application's data structures.

C influenced several other languages and derivatives, such as C++, Objective-C used by Apple, C# used by Microsoft, and Java extensively used in corporate environments and also by Android. Ritchie and Thompson used C to write UNIX. Unix has been influential in establishing computing concepts and principles that have been widely adopted.

In an interview from 1999, Ritchie clarified that he saw Linux and BSD operating systems as a continuation of the basis of the Unix operating system, and as derivatives of Unix:[17]

I think the Linux phenomenon is quite delightful, because it draws so strongly on the basis that Unix provided. Linux seems to be among the healthiest of the direct Unix derivatives, though there are also the various BSD systems as well as the more official offerings from the workstation and mainframe manufacturers.

In the same interview, he stated that he viewed Unix and Linux as "the continuation of ideas that were started by Ken and me and many others, many years ago."[17]


In 1983, Ritchie and Thompson received the Turing Award "for their development of generic operating systems theory and specifically for the implementation of the UNIX operating system".[18] Ritchie's Turing Award lecture was titled "Reflections on Software Research".[19] In 1990, both Ritchie and Thompson received the IEEE Richard W. Hamming Medal from the Institute of Electrical and Electronics Engineers (IEEE), "for the origination of the UNIX operating system and the C programming language".[20]

In 1997, both Ritchie and Thompson were made Fellows of the Computer History Museum, "for co-creation of the UNIX operating system, and for development of the C programming language."[21]

On April 21, 1999, Thompson and Ritchie jointly received the National Medal of Technology of 1998 from President Bill Clinton for co-inventing the UNIX operating system and the C programming language which, according to the citation for the medal, "led to enormous advances in computer hardware, software, and networking systems and stimulated growth of an entire industry, thereby enhancing American leadership in the Information Age".[22][23]

In 2005, the Industrial Research Institute awarded Ritchie its Achievement Award in recognition of his contribution to science and technology, and to society generally, with his development of the Unix operating system.[24]

In 2011, Ritchie, along with Thompson, was awarded the Japan Prize for Information and Communications for his work in the development of the Unix operating system.[25]


Dennis Ritchie (right) with Doug McIlroy (left) in May 2011

Ritchie was found dead on October 12, 2011, at the age of 70 at his home in Berkeley Heights, New Jersey, where he lived alone.[3] First news of his death came from his former colleague, Rob Pike.[26][27][28] He had been in frail health for several years following treatment for prostate cancer and heart disease.[3][26][29][30] News of Ritchie's death was largely overshadowed by the media coverage of the death of Apple co-founder Steve Jobs, which occurred the week before.[31]


Following Ritchie's death, computer historian Paul E. Ceruzzi stated:[32]

Ritchie was under the radar. His name was not a household name at all, but... if you had a microscope and could look in a computer, you'd see his work everywhere inside.

In an interview shortly after Ritchie's death, long-time colleague Brian Kernighan said Ritchie never expected C to be so significant.[33] Kernighan told The New York Times "The tools that Dennis built—and their direct descendants—run pretty much everything today."[34] Kernighan reminded readers of how important a role C and Unix had played in the development of later high-profile projects, such as the iPhone.[35][36] Other testimonials to his influence followed.[37][38][39][40]

Reflecting upon his death, a commentator compared the relative importance of Steve Jobs and Ritchie, concluding that "[Ritchie's] work played a key role in spawning the technological revolution of the last forty years—including technology on which Apple went on to build its fortune."[41] Another commentator said, "Ritchie, on the other hand, invented and co-invented two key software technologies which make up the DNA of effectively every single computer software product we use directly or even indirectly in the modern age. It sounds like a wild claim, but it really is true."[42] Another said, "many in computer science and related fields knew of Ritchie's importance to the growth and development of, well, everything to do with computing,..."[43]

The Fedora 16 Linux distribution, which was released about a month after he died, was dedicated to his memory.[44] FreeBSD 9.0, released January 12, 2012, was also dedicated in his memory.[45]

Asteroid 294727 Dennisritchie, discovered by astronomers Tom Glinos and David H. Levy in 2008, was named in his memory.[46] The official naming citation was published by the Minor Planet Center on 7 February 2012 (M.P.C. 78272).[47]


Notable works

Publications and academic papers

Ritchie has been the author or contributor to about 50 academic papers, books and textbooks and which have had over 15,000 citations.[49]

Here are some of his most cited works:

See also


  1. ^ "IEEE Emanuel R. Piore Award Recipients" (PDF). IEEE. Archived from the original (PDF) on November 24, 2010. Retrieved March 20, 2021.
  2. ^ "Dennis Ritchie". Computer History Museum. Archived from the original on January 3, 2015. Retrieved January 5, 2015.
  3. ^ a b c d Lohr, Steve (October 12, 2011), "Dennis Ritchie, Programming Trailblazer, Dies at 70", The New York Times, archived from the original on July 25, 2021, retrieved October 13, 2011, Dennis M. Ritchie, who helped shape the modern digital era by creating software tools that power things as diverse as search engines like Google and smartphones, was found dead on Wednesday at his home in Berkeley Heights, N.J. He was 70. Mr. Ritchie, who lived alone, was in frail health in recent years after treatment for prostate cancer and heart disease, said his brother Bill.
  4. ^ Keister, William; Ritchie, Alistair E.; Washburn, Seth E. (1951). The Design of Switching Circuits (eighth printing Sep. 1963 ed.). Princeton, NJ: D. Van Nostrand Co., inc. Members of the Technical Staff, Bell Telephone Laboratories
  5. ^ a b Miller, Stephen (October 14, 2011). "Pioneer Programmer Shaped the Evolution of Computers". Wall Street Journal. ISSN 0099-9660. Retrieved March 3, 2018.
  6. ^ Keill, Liz (February 1, 2011). "Berkeley Heights man wins Japan Prize for inventing UNIX operating system". Independent Press. Retrieved October 17, 2011. Ritchie, 69, has lived in Berkeley Heights for 15 years. He was born in Bronxville, New York, grew up in Summit and attended Summit High School before going to Harvard University.
  7. ^ van Renesse, Robbert (January 2014). "The First SIGOPS Dennis M. Ritchie Doctoral Dissertation Award". ACM SIGOPS Operating Systems Review. 48 (1): 100. doi:10.1145/2626401.2626421. S2CID 34452214.
  8. ^ a b Brock, David C. (June 19, 2020). "Discovering Dennis Ritchie's Lost Dissertation". CHM. Retrieved June 20, 2020.
  9. ^ Brailsford, David F.; Kernighan, Brian W.; Ritchie, William A. "How did Dennis Ritchie Produce his PhD Thesis? A Typographical Mystery" (PDF). doi:10.1145/3558100.3563839. Retrieved March 15, 2023.
  10. ^ Ritchie, Dennis M. (October 1984). "The Evolution of the Unix Time-sharing System". Bell Laboratories. Retrieved October 31, 2016.
  11. ^ Ritchie, Dennis (April 1993). "The Development of the C Language". Bell Labs. Retrieved October 31, 2016.
  12. ^ a b "Dabbling in Cryptography". Bell Labs. May 5, 2000. Retrieved November 14, 2016.
  13. ^ Musil, Steven (October 13, 2011). "Dennis Ritchie, father of C programming language, dies". cnet. Archived from the original on December 9, 2021.
  14. ^ "Pioneer Programmer Shaped the Evolution of Computers", Wall Street Journal, October 14, 2011, p.A7
  15. ^ McIlroy, M. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. 139. Archived (PDF) from the original on May 4, 2014.
  16. ^ "The C Programming Language, Second Edition", Bell Telephone Laboratories, Inc., 1988, p.xi
  17. ^ a b Benet, Manuel (1999). "Interview With Dennis M. Ritchie".
  18. ^ "A.M. Turing Award Laureate - Dennis M. Ritchie". ACM. Retrieved April 2, 2019.
  19. ^ Ritchie, Dennis M. (1987), "1983 Turing Award Lecture: Reflections on Software Research", ACM Turing Award Lectures: The First Twenty Years 1666–1985, ACM Press Anthology Series, Addison-Wesley Publishing Company, pp. 163–169, doi:10.1145/1283920.1283939, ISBN 9781450310499, retrieved January 30, 2012
  20. ^ "IEEE Richard W. Hamming Medal Recipients" (PDF). IEEE. Archived (PDF) from the original on June 20, 2010. Retrieved May 29, 2011.
  21. ^ CHM. "Dennis Ritchie — CHM Fellow Award Winner". Archived from the original on April 3, 2015. Retrieved March 30, 2015.
  22. ^ "Ritchie and Thompson Get National Medal of Technology". Bell Labs. December 8, 1998. Archived from the original on March 27, 2006. Retrieved September 6, 2006.
  23. ^ "Ritchie and Thompson Receive National Medal of Technology from President Clinton". Bell Labs. April 27, 1999. Archived from the original on October 11, 2003. Retrieved November 4, 2003.
  24. ^ "Dennis Ritchie, Bell Labs Researcher and Co-Inventor of Unix, Receives 2005 Industrial Research Institute Achievement Award". Alcatel-Lucent Press Release. November 15, 2005. Archived from the original on February 4, 2014. Retrieved February 8, 2012.
  25. ^ Evangelista, Benny (January 25, 2011). "Ken Thompson, Dennis Ritchie win Japan Prize". San Francisco Chronicle.
  26. ^ a b "Unix creator Dennis Ritchie dies aged 70". BBC News. October 13, 2011. Retrieved October 14, 2011. Pioneering computer scientist Dennis Ritchie has died after a long illness. ... The first news of Dr Ritchie's death came via Rob Pike, a former colleague who worked with him at Bell Labs. Mr Ritchie's passing was then confirmed in a statement from Alcatel-Lucent which now owns Bell Labs.
  27. ^ Pike, Rob (October 12, 2011), (untitled post to Google+), archived from the original on February 17, 2018, retrieved October 14, 2011, I just heard that, after a long illness, Dennis Ritchie (dmr) died at home this weekend. I have no more information.
  28. ^ "Summary Box: Dennis Ritchie, pioneer in computer programming at Bell Labs, dies at 70", The Washington Post, Associated Press, October 13, 2011, archived from the original on December 24, 2018, retrieved October 14, 2011, NOT KNOWN: Alcatel-Lucent confirmed his death to The Associated Press but would not disclose the cause of death or when Ritchie died.
  29. ^ Gallagher, Sean (October 13, 2011). "Dennis Ritchie, Father of C and Co-Developer of Unix, Dies". Wired. Retrieved October 13, 2011.
  30. ^ Binstock, Andrew. "Dennis Ritchie, in Memoriam". Dr. Dobb's Journal. Retrieved October 14, 2011.
  31. ^ Srinivasan, Rajeev (October 25, 2011). "Dennis Ritchie, a tech genius as great as Steve Jobs". Firstpost. Retrieved December 4, 2017.
  32. ^ Langer, Emily (October 14, 2011). "Dennis Ritchie, founder of Unix and C, dies at 70". Washington Post. Retrieved November 3, 2011.
  33. ^ Prasad, Shishir (November 4, 2011). "No one thought 'C' would become so big: Brian Kernighan". Forbes India. Retrieved November 28, 2011. Q Did Dennis Ritchie or you ever think C would become so popular? [Kernighan] I don't think that at the time Dennis worked on Unix and C anyone thought these would become as big as they did. Unix, at that time, was a research project inside Bell Labs.
  34. ^ Lohroct, Steve (October 13, 2011). "Dennis Ritchie, 70, Dies, Programming Trailblazer". The New York Times. Retrieved November 14, 2016.
  35. ^ "Myths of Steve Jobs". Deccan Herald. November 28, 2011. Archived from the original on July 27, 2013. Retrieved November 28, 2011. Dennis Ritchie, the inventor of the C language and co-inventor of the Unix operating system, died a few days after Steve Jobs. He was far more influential than Jobs.
  36. ^ Datta, Subhajit (November 14, 2011). "The tale of three deeply different technologists". The Hindu. Archived from the original on November 16, 2011. Retrieved November 28, 2011.
  37. ^ Cardinal, David (November 2, 2011). "Dennis Ritchie, creator of C, bids "goodbye, world"". Extreme Tech. Retrieved November 28, 2011. The book came off the shelf in service of teaching another generation a simple, elegant way to program that allows the developer to be directly in touch with the innards of the computer. The lowly integer variable—int—has grown in size over the years as computers have grown, but the C language and its sparse, clean, coding style live on. For that we all owe a lot to Dennis Ritchie.
  38. ^ "Dennis Ritchie and John McCarthy: Dennis Ritchie and John McCarthy, machine whisperers, died on October 8th and 24th respectively, aged 70 and 84". The Economist. November 5, 2011. Retrieved November 28, 2011. NOW that digital devices are fashion items, it is easy to forget what really accounts for their near-magical properties. Without the operating systems which tell their different physical bits what to do, and without the languages in which these commands are couched, the latest iSomething would be a pretty but empty receptacle. The gizmos of the digital age owe a part of their numeric souls to Dennis Ritchie and John McCarthy.
  39. ^ "The Strange Birth and Long Life of Unix". Newswise. November 23, 2011. Retrieved November 28, 2011. Four decades ago, Ken Thompson, the late Dennis Ritchie, and others at AT&T's Bell Laboratories developed Unix, which turned out to be one of the most influential pieces of software ever written. Their work on this operating system had to be done on the sly, though, because their employer had recently backed away from operating-systems research.
  40. ^ Das, Shyamanuja (November 1, 2011). "The forgotten tech luminaries: The new generation of the digital age owe a part of their numeric souls to Dennis Ritchie and John McCarthy". Archived from the original on July 3, 2016. Retrieved November 28, 2011. UNIX, to the development of which Ritchie greatly contributed, and whose C made it possible it to be ported to other machines, is, even today, in its different avatars, the de facto OS for anything that is mission critical. Solaris, AIX, HP-UX, Linux—all these are derived from UNIX.
  41. ^ Duncan, Geoff (October 13, 2011). "Was Dennis Ritchie more important than Steve Jobs?". Digital Trends. Retrieved November 14, 2016.
  42. ^ Perlow, Jason (October 9, 2015). "Without Dennis Ritchie, there would be no Steve Jobs". Retrieved November 14, 2016.
  43. ^ "What Can We Learn From Dennis Ritchie?". TechCrunch. October 15, 2011. Retrieved November 14, 2016.
  44. ^ Phoronix. "Red Hat Releases Fedora 16 "Verne"". Retrieved November 8, 2011.
  45. ^ The FreeBSD project. "FreeBSD-9.0 Announcement". Retrieved January 12, 2012.
  46. ^ "294727 Dennisritchie (2008 BV41)". Minor Planet Center. Retrieved September 12, 2019.
  47. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved September 12, 2019.
  48. ^ Kernighan, Brian W.; Ritchie, Dennis M. (1978). The C Programming Language. Englewood Cliffs, N.J.: Prentice-Hall. ISBN 978-0131101630. OCLC 3608698.
  49. ^ "Dennis Ritchie". Retrieved February 2, 2021.
  50. ^ Kernighan, Brian W.; Ritchie, Dennis (March 22, 1988). C Programming Language: C PROGRAMMING LANG _p2. Prentice Hall. ISBN 978-0-13-308621-8.
  51. ^ "Dennis Ritchie". Retrieved February 2, 2021.
  52. ^ Ritchie, Dennis M.; Thompson, Ken (2001), Hansen, Per Brinch (ed.), "The Unix Time-Sharing System", Classic Operating Systems: From Batch Processing To Distributed Systems, New York, NY: Springer, pp. 195–220, doi:10.1007/978-1-4757-3510-9_11, ISBN 978-1-4757-3510-9, retrieved February 2, 2021
  53. ^ Stevens, W. Richard; Rago, Stephen A. (2008). Advanced Programming in the UNIX Environment. Addison-Wesley. ISBN 978-0-321-52594-9.